Process for preparing 2, 3-dimethylheptene-2-one-6



Patented Dec. 15, 1953 PROCESS FOR PREPARING 2,3-DIMETHYL-HEPTENE-2-ONE-6 Walter Kimel, Highland Park, N. J assignor toHoflmann-La Roche Inc., Roche Park, Nutley, N. .l'., a corporation ofNew Jersey No Drawing. Original application June 10, 1952,

Serial No. 292,730. Divided and this application November 29, 1952,Serial No. 323,334

2 Claims. 1

This invention relates to a novel chemical compound, and to process ofpreparing and con verting said compound. More particularly, theinvention is concerned with the new substance 1,1,2 trimethyl propenZ-yl 3 oxobutanoate which can be represented by the formula CHsCOCHzCOOC(CI-Is) 2C (CH3) =CI-I2. T hi 5 substance can be prepared by condensing2,3-dimethyl-buten-3-ol-2 with diketene, and the product can beconverted by heating (with loss of carbon dioxide) into2,3-dimethyl-hepten-2- one-6. The latter can be converted to methyleitral, methyl-geraniol or pseudoirone by known processes, and thus theinvention is of interest to the pharmaceutical, perfume and soapindustries.

The invention is further disclosed in the following example, which isillustrative but not limitative thereof.

EXAMPLE In a flask equipped with a stirrer, a thermometer, a droppingfunnel, and a drying tube, 0.5 g. of sodium was reacted with 200 g. (2.0mol) of 2,3-dimethyl-buten-3-ol-2. The solution was cooled to C. and 202g. (2.4 mols) of diketene was added slowly, with efficient stirring,during five hours, while maintaining the temperature at 10 C. Themixture was then stirred for 24 hours at 10 C.

The resulting dark orange solution was diluted with 200 cc. of tolueneand extracted four times with 200 cc. portions of saturated sodiumbicarbonate solution, and then washed with water until neutral. Theorganic solution was dried 2 over calcium sulphate, and. concentrated invacuo. The residue was fractionated under reduced pressure to yield1,1,2-trimethyl-propen- 2-yl 3-oxobutanoate, B. P. (4 mm.) -85 0.; n:1.4461.

In a one-liter-3-neck flask, connected to a gas meter through anefiicient reflux condenser, and also equipped with a stirrer andthermometer, was placed 2'76 g. (1.5 mols) of 1,1,2-trimethylpropen-Z-yl3-oxobutanoate. The flask was heated in an oil bath at -170 C. Evolutionof carbon dioxide commenced at about 125 C., and was complete after 3hours at to C. The product was purified by distillation under reducedpressure, yielding 2,3-dimethyl-hepten 2-one-6; B. P. 74-7'7 C. (9 mm.)n :1.4480.

This application is a division of my copending application Ser. No.292,730, filed June 10, 1952.

I claim:

1. A process which comprises condensing diketene with2,3-dimethyl-buten-3-o1-2 and decarboxylating the condensation productto produee 2,3dimethyl-hepten2'one-6.

2. A process of preparing 2,3-dimethy1-hepten- 2-one-6 which comprisesheating 1,1,2-trimethylpropen-Z-yl 3-oxobutanoate to eliminate carbondioxide therefrom.

WALTER KIMEL.

References Cited in the file Of this patent FOREIGN PATENTS Number

1. A PROCESS WHICH COMPRISES CONDENSING DIKETENE WITH2,3-DIMETHYL-BUTEN-3-OL-2 AND DECARBOXYLATING THE CONDENSATION PRODUCTTO PRODUCE 2,3-DIMETHYL-HEPTEN-2-ONE-6.